In the field of endodontics, one of the most important and delicate procedures is that of cleaning or extirpating a root canal to provide a properly dimensioned cavity while essentially maintaining the central axis of the canal. This step is important in order to enable complete filling of the canal without any voids and in a manner which prevents the entrapment of noxious tissue in the canal as the canal is being filled.
In cleaning and enlarging the root canal, instruments called files or reamers are used. Commonly, both files and reamers have flutes which spiral along a portion of the instrument length, and whether the instrument is a file or a reamer is determined by the pitch of the flutes. A greater pitch enables the instrument to cut better in a rotary mode, hence a reamer, and a lesser pitch enables the instrument to cut better in the reciprocating mode, hence a file. During a cleaning and shaping operation performed with such a file or reamer, the instrument is normally rotated and moved into and out of the root canal along the longitudinal axis of the instrument.
A widely used type of file or reamer is known by the designation "K-file" or "K-reamer". These instruments are made from a tapered rod which may be triangular or square in cross-section. The instruments are fabricated from the rods by twisting the rod to form a generally helical flute along the working portion of the rod, or the helical flute may be machined into the shaft.
The K-type instruments have several disadvantages. First, the instruments have a tendency to transport the central axis of a curved canal as the instrument cuts, mostly where the greatest pressure is exerted against the wall of the canal. Second, as the instruments are continuously rotated, the blades can become locked into the canal causing the instrument to break.
Finally, when modifications are made on conventional files and reamers to limit the tendency of the instrument to act as a screw or to diminish canal transportation, the tissue removal efficiency is generally sacrificed, particularly when a substantially non-circular canal is encountered as in a "fin" or "anastomosis."
It is therefore an object of the invention to provide an improved endodontic dental instrument.
Another object of the invention is to provide an endodontic dental instrument which enables improved removal efficiency of material from a root canal.
A further object of the invention is to provide an endodontic dental instrument having high tissue removal efficiency for non circular and/or curved root canals in addition to generally straight, circular canals.